Research explores new ways to study bacterial pollution

CORVALLIS - Scientists at Oregon State University are testing new ways to determine sources of bacterial contamination in Tillamook Bay, which could have wide application around the world.

"We need to know where the pollution is coming from - cows, sewage treatment facilities or failing septic tanks," said Jim Moore, professor and chair of the OSU Department of Bioresource Engineering. "If we are able to go back and find the sources of the pollution, we can then do what we need to do to fix the problem."

However, there are no reliable methods to determine the sources of fecal coliform bacteria contamination.

Is the bacterial pollution found in the bay from cows or humans or both? At what times of year are there problems? Does sewage treatment and septic tank contamination contribute significantly to the problem? Questions such as these are hindering efforts to solve chronic bacterial contamination problems in Tillamook Bay and many other places around the globe.

With a growing human population and large dairy industry in the Tillamook watershed, the waters of Tillamook Bay frequently exceed government water quality standards for fecal coliform bacterial contamination. Shellfish harvest and other estuary-dependent species are adversely affected.

Moore and his graduate student Robert Bower are investigating whether patterns of antibiotic resistance in fecal bacteria from cows and humans are different enough that they can be used to trace the sources of bacterial pollution in Tillamook Bay.

"Microorganisms in cows have a different antibiotic resistance than those same organisms in people," Moore said. "In this study we are analyzing the resistance pattern of one organism, fecal streptococci. Cows take different drugs than we do, therefore may have different resistance patterns to antibiotics."

Bower is growing fecal streptococci bacteria from cows and humans in the presence of five different antibiotics, each at four different strengths. He and Moore will look at the overall patterns in which the bacteria are killed by the antibiotics, and analyze them using a sophisticated statistical method called "discriminate analysis."

"Hopefully, the bacteria from cows will behave differently than human bacteria when grown in the presence of antibiotics. We hope to be able detect different patterns of kill in each, and we will be able to determine a characteristic pattern for each source, human or cow," said Moore.

Meanwhile, in the Department of Microbiology at OSU, doctoral student Anne Bernhard and her advisor, assistant professor Kate Field, are investigating whether a type of fecal bacteria called "bacteroides," found in both humans and cows, have detectable differences in their DNA. They chose this group of bacteria because it doesn't survive well outside of the gut, and is therefore a good indicator of fecal contamination at a given instant in time.

"We are looking for differences in patterns of the DNA in pieces of a gene in human bacteroides versus cow bacteroides," explained Bernhard. "If there are differences, maybe someday we can devise a user-friendly kit for water quality labs to be able tell whether the bacteria is from a human or a cow."

If either research project is successful, the tests devised might be used to solve bacterial water pollution mysteries all over the world.

"There are huge applications in water pollution control if we perfect a method to pinpoint the source of bacterial pollution," said Moore. "New techniques will give regulators, land managers or extension programs a little bit more leverage to get action to alleviate a problem, whether it be in an estuary, a chicken processing plant, a swimming beach or a water treatment plant intake site."

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